For all my builds I have been soaking the wood I intend to bend in plain water and this has been working fine so far. However in many other builds I have read the builder uses a mixture of water and either ammonia (Windex) or vinegar. Am I missing something? What does mixing these additives do that plain water doesn't?

Give a man a plane and he'll fly for a day.
Teach a man to build a plane and he'll fly for a lifetime.